Andrea has a tutorial here http://www.penthesilea.ch/yabbutils/save-instr/ with details of how to back up your database, though this patch doesn't require any db modifications (I dont think anyway, I havent actually looked at it) so it should be very low risk.

do back up though, you should always back up just in case your host messes up or something like that.

If you see "yabbse.org Bugs" in the list, click on "[ Browse ]" next to it. Otherwise, type "yabbse.org Bugs" in for the server name, and "http://www.yabbse.org/packages/bugs" for the URL. (no slash at the end!) Now, click on "[ Browse ]" next to it

You should see a list of fixes. Find the section for the version you currently have installed, and pick the mod titled "YaBB SE YOUR VERSION to YaBB SE 1.5.5 Update" and click "[ Download ]".

Now click "[ Back ]" and then "[ Back ]". Now click "[ Browse YaBBpaks ]".

Find the mod you downloaded in the list. (it might be the only thing in there...) Click the "[ Apply Mod ]" next to it.

Click "[ Proceed ]". Then, "[ Test (recommended) ]".

For every file listed in large print, find it in your FTP. Make sure it is, TEMPORARILY chmod'd to 777. This makes it so the package manager can update them. You will also need to make the folders they are in 777 so it can make backups.

If you don't get any "not found" errors, it should install properly. Click "[ Apply Mod ]". If you get any errors, you probably forgot to chmod something to 777.

ob_end_clean(); $request = mysql_query("Can ya tell me how important these particular ones are and what I should do about them? This was on a "test install" so there's no harm done but I would like to get the security updated.